Special reference is made to boxes destined to contain coils of large quantities of metal wire, in particular welding wire, with weights going from about 50 kg. up to 400 kg.
The use of such large coils means that automatic welding machines, which are fed with the wire, can operate for continuous and extensive time periods. The functions, feeding-in and unwinding modes, as well as the type of stresses the boxes are subject to, all lead to very considerable specialisation in their design, i.e. very different to the design specifications required for other types of containers or packaging.
First of all, the continuous wire is deposited inside the container in such a way that it can be dispensed there-from without risk of tangling; special geometrical arrangements are already known for introducing the wire (not of direct interest to the present invention, which uses known techniques), as are central reels which prevent the wire from moving about during transport. The wire is introduced into the box by special machines having platforms on which the empty boxes are placed and from which, once filled, they are removed with the help of special machines (due to their weight). The box must therefore be of an easily manoeuvrable type, whether empty or full.
The box must also be sufficiently sturdy to withstand lateral stresses, which might otherwise cause unacceptable deformations in the shape of the box itself and the coil of wire contained therein, as well as axial stresses, so that several boxes can be piled one on top of another without crushing any one box. These stresses may be of quite large entity, especially if one considers the amount of movement the boxes are subject to at the various phases, such as when they are at the wire producer's plant, when they are being loaded or unloaded (into a lorry, train or even a ship), as well as when they are being delivered to the eventual user.
The box must also be conformed so that it does not in any way negatively influence the unwinding of the wire.
Before it is filled, the box has to be as easy as possible to move and store. Once the wire has been used up, the box is not generally regenerated for further use, so it should also be economical and easy to dispose of.
A first known type of box of the above type is cylindrical (in effect a piece of tubing) which is provided with ends, top and bottom, generally having metal ribs to reinforce the box itself. Sometimes these boxes are provided with handles, either made of metal or other materials. These boxes are made of a specially tough material, which, however, is expensive. Further disadvantages of these boxes are that they have to be disposed of selectively, and are just as big when empty as when full.
Generally cubic boxes have been devised which are made up from folded card. These are economical, and can be easily and efficiently destroyed by the user, but are also only limitedly resistant and are therefore not favoured by producers as they cause problems during movement, nor are they preferred by users who often receive them in a deformed state, which renders the wire difficult to use. There exists a further problem, connected with the possible corrosion of the wire which usually happens during sea transport which at times can last for weeks or even months; none of the existing boxes obviates this problem.